The present invention relates to the pulse detection technique in the semiconductor data processing apparatus and of detecting pulses in response to rotation of a crank shaft in an engine control apparatus and more particularly to the technique effective for application to engine control of a gasoline-engined car and a hybrid car, for example.
Heretofore, the engine control apparatus is supplied with signals from various sensors such as a crank shaft sensor, a water temperature sensor, an atmosphere temperature sensor and the like to control the fuel injection and the ignition timing in optimum. A crank signal which is a signal produced from the crank shaft sensor is a train of pulses produced at intervals of predetermined angle corresponding to rotation of a crank shaft of an engine. The engine control apparatus produces a multiple clock (which has the period equal to a submultiple of the multiple of a period of the crank signal) having a frequency equal to the multiple of tire frequency of the crank signal, for example, and the multiple clock is counted up by a crank counter of which the count value represents a rotation angle (so-called crank angle) of the crank shaft, so that the control synchronized with rotation of the engine is made on the basis of the value of the crank counter. By doing so, the crank angle can be grasped with finer resolution as compared with the original crank signal.
The crank signal has a toothless part (reference position part) where pulses are lacking on the way of the pulse train. For example, in the toothless structure in which two pulses are lacking every 60 pulses in the crank signal the toothless part appears two times in one cycle (crank rotation angle of 720 degrees) of the engine, that is, one toothless pan appears once every 360 degrees of the crank rotation angle. In the engine control, detection of the toothless part is made to the pulse train of the crank signal in order to make the control synchronized with tire engine cycle.
In order to detect the toothless part, the multiple clock signals having the frequency equal to the multiple of the frequency of the crank signal for example, are counted up for each pulse of the crank signal to thereby measure a pulse interval of the crank signal. When the count value at the pulse interval of the crank signal being measured this time is equal to or larger than a reference value obtained by multiplying the count value at the pulse interval where there is no toothless part by a predetermined toothless-part judgment ratio, it is judged that the pulse interval being measured this time is the toothless part. The toothless-part detection operation and the like are described in JP-A-2005-133614, JP-A-2001-271700, JP-A-2006-125240 and JP-A-2010-025017.